1. Field of the Invention
The present invention is generally in the field of semiconductor fabrication. More specifically, the invention is in the field of fabrication of capacitors in semiconductor dies.
2. Background Art
High performance mixed signal and RF circuits require high-density integrated capacitors. Metal-insulator-metal (“MIM”) capacitors can be considered for use in the fabrication of integrated mixed signal and RF circuits on semiconductor dies. However, typical MIM capacitors have low capacitance density and since RF and mixed signal applications require high capacitance values, the die area consumed by typical MIM capacitors is too large, resulting in increased die cost to the manufacturer.
In a conventional MIM capacitor, a MIM capacitor dielectric is situated between bottom and top metal plates, which form electrodes of the MIM capacitor. The MIM capacitor dielectric is distinct from an interlayer dielectric layer, which is formed between adjacent interconnect metal layers of a semiconductor die. The capacitance density of the conventional MIM capacitor is approximately 1.0 femtofarad (“fF”)/um2 for a conventional MIM capacitor dielectric comprising silicon oxide or silicon nitride. In order to increase the capacitance density of the conventional MIM capacitor, a dielectric material having a higher dielectric constant can be used or the thickness of the MIM capacitor dielectric can be reduced.
However, the breakdown voltage and the leakage current of the dielectric material limit how thin the MIM capacitor dielectric can be. For example, in a conventional MIM capacitor dielectric comprising silicon nitride, the breakdown voltage and leakage current of the silicon nitride prevent the thickness of the conventional MIM capacitor dielectric from being thinner than approximately 615.0 Angstroms with significantly reducing reliability.
Thus, there is a need in the art for increased capacitance density in a MIM capacitor.